FIG. 1 shows a set of stations Si interconnected by a radio network where the resources are organized in time/frequency slots as shown in FIG. 2. In a given time slot and a given frequency some stations will transmit to some of their neighboring destination stations. For a given cycle, a logical channel C is allocated for a time slot K.
The problem posed is to allocate the slots and the frequencies to transmitter stations (and to a subset of their neighboring stations, called destination stations) in a distributed manner by best using the available resources, i.e. by allowing a maximum number of transmitters to use the same slot while conforming to the following rules:                a station is either a transmitter or a receiver;        if the station is a transmitter, then the destinations are receivers in the slot and the frequency of the transmitter, and a station may only be a receiver for a single channel and a single transmitter;        if the station is a receiver from a transmitter on a channel, there are no other stations neighboring this station that are a transmitter on the same channel apart from the transmitter being listened to.        
It is also known to orthogonalize transmissions in a slot by using other types of transmission to the transmission at a given frequency, for example orthogonalized frequency jumps, CDMA (Code Division Multiple Access) codes.
The organization of transmissions in slots requires a synchronization function that is assumed to exist, for example the GPS system or any other time distribution system.
Various solutions are currently being proposed in the literature or in existing systems for the problem of allocation.
The situation with the most conventional allocation is that where the assignment of time-frequency allocations is carried out by a base station; the topology of the network is not necessarily star-shaped. This base station manages the assignments through requirements and priorities of the features of the stations.
This solution is adopted (partly or completely) by a majority of civilian protocols using TDMA (time division multiple access 802.16, 802.11 in directed mode etc.). For reasons of reactivity and robustness, it is only conceivable for multilink networks of a moderate extent.
In the families of solutions for ad hoc networks, various methods are found that can be adapted more or less to the topology and to the traffic demand.
The simplest systems have a first-level allocation that is predefined and assigned to groups of stations depending on predictable features of demand and deployment. Once this allocation has been assigned, there are rules for using this allocation in the group, these rules being able to accept collisions or arrange signaling to settle the conflicts.
To resolve situations in the networks with a large number of hops, many decentralized solutions have been proposed, only some of which are mentioned below.
A first family organizes the transmission in a reservation phase, which might be in contention, followed by a transmission phase. The reservation-transmission cycle is periodically repeated.
Another family of solutions consists in exchanging signaling on a particular resource called the preallocated or dynamically allocated signaling channel. This signaling enables the resources used by a station to be known and hence conflicts to be detected, and verification of whether a resource can be allocated, without frequently indicating how to arbitrate these conflicts or how to assign the allocations (except partly or in the framework of a preallocation).
Another family of solutions enables the absence of conflict to be guaranteed without for all that determining an allocation to the stations. It is based on signaling that allows a station to identify which stations are in conflict (this depending on the type of transmission envisaged, point to point (one station to a neighbor or an activation link), broadcast (one station to all its neighbors or an activation node). A pseudo-random method then allows it to be known, for a given slot at a station, whether the station wins the right to use the slot over competing stations. The method guarantees the absence of conflict but does not provide stations with deterministic knowledge of the slots it can use. In addition, in one sense it is sub-optimal, as some slots cannot be used due to the multi-hop character of the network and to various constraints between stations. This method is used in the 802.16 standard and in the HAMA, LAMA and NAMA protocols by Lichun Bao and J. J. Garcia-Luna-Aceves described in the publications “Channel Access Scheduling for Ad-Hoc Networks” Journal of Parallel and Distributed Computing, Special Issue on Wireless and Mobile Ad Hoc Networking and Computing, 2002 and “Distributed Channel Access Scheduling for Ad Hoc Networks”, or again in the patent application US 2002/0167960.
Another family of solutions works on a preliminary network structure at two levels. For example, a distributed procedure for structuring the network in groups or clusters. These clusters receive a family allocation (of slots) and this allocation is dynamically managed in this cluster (reducing to a base station type management) and comes down to a centralized allocation. General rules are used for the allocation of clusters, for example assigning a frequency (a channel, a CDMA code) to a cluster such that interfering clusters have different frequencies. (For example M Gerla and C. R Lin In IEEE Commun. September 97 “Adaptive clustering for mobile Wireless networks”). However, such a solution has some limits. First of all, it is necessary to prestructure the allocations into independent groups to be able to allocate the clusters (here a group is the set of allocations at a frequency, but when there are few frequencies it is necessary to use time division). For the number of groups necessary depends on the topology. There lies a difficulty. Moreover, the demands between the clusters are not necessarily equivalent. The preallocation per group may lead to insufficiencies in one group and a lack in others. Finally, in the case of changing the clusterization, it is the set of allocations that are affected and hence requires a reallocation.
The last family of allocations mentioned is the SDTMA allocation by J. Grönkvist “Distributed STDMA in Ad hoc network” et “Interference-Based Scheduling in Spatial Reuse TDMA” J. Grönkvist Doctoral Thesis Stockholm, Sweden 2005. In this thesis the author describes a decentralized method for allocating nodes or links by negotiation and arbitration of conflicts between the stations. The arbitration takes account of the traffic through a priority function. Furthermore, the interference conditions between transmitters and receivers aims to take into account a more detailed interference model than the simple neighborhood used in the invention described below, the model being known to the person skilled in the art.